使用ajax时无法使用的数据库功能

Question

I have a function that pulls information from a mysql database. The function has been tested and works when calling it from a regular html form submit button. However, I have been trying to implement ajax, and I call the exact same function, but it isn't working, and I have no idea why.

Here is the database function. I have removed unnecessary code to make it more readable.

function itemUPCsearch($upc)
    {
        $conn = localConnection();
        $query = "SELECT Items.UPC, availability, description, price, brand, perqty, item_type, unit_type, size, discount, serv_per_cal, calories, calories_from_fat, total_fat, saturated_fat, trans_fat, cholesterol, sodium, total_carbohydrate, dietary_fiber, sugars, protein, vitamins, ingredients, full_image_path FROM Items LEFT JOIN Nutrition ON Items.UPC = Nutrition.UPC LEFT JOIN item_pic P ON P.UPC = Items.UPC WHERE Items.UPC = ?";
        $stmt = mysqli_prepare($conn, $query);
        mysqli_stmt_bind_param($stmt, "s", $upc);
        mysqli_stmt_execute($stmt);
        mysqli_stmt_bind_result($stmt, $upc, $avail, $desc, $price, $brand, $perqty, $itype, $utype, $size, $discount, $servpercal, $cal, $calfromfat, $totfat, $satfat, $tranfat, $chol, $sod, $totcarb, $dietfib, $sugar, $prot, $vit, $ing, $image);



        while(mysqli_stmt_fetch($stmt))
        {

                // Execution never makes it inside this loop
                // Do stuff here (Code has been removed as it is not relevant
                // To this question)

        }
        mysqli_stmt_close($stmt);
        closeConnection($conn);

        return $searchItems;
    }

As far as I can tell, everything seems to be ok. I have done a print_r on $conn and $stmt, and I get back what I would expect. I compared these with the print_r of those objects on working functions and I get back the same results. I have printed the result of the execute function and it is returning true. The query never changed from when it worked with the regular form submit. The value $upc that was passed in is correct, and there is an entry for this in the database. In fact, when I copy and paste the query with the upc value into mysql, I get back the correct result. For some reason though, the function never makes it inside the while loop, even though it makes it there when calling this same function using a form post while passing in the same upc.

Here is my ajax script:

function loadCart(itemID,cart) {
  var httpRequest;
  makeRequest(itemID,cart);

  function makeRequest(itemID,cart) {
    if (window.XMLHttpRequest) { // Mozilla, Safari, ...
      httpRequest = new XMLHttpRequest();
    } else if (window.ActiveXObject) { // IE
      try {
        httpRequest = new ActiveXObject("Msxml2.XMLHTTP");
      } 
      catch (e) {
        try {
          httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
        } 
        catch (e) {}
      }
    }

    if (!httpRequest) {
      alert('Giving up :( Cannot create an XMLHTTP instance');
      return false;
    }

    httpRequest.onreadystatechange = fillTheCart;
    httpRequest.open('GET', "../controller/addToCartAjaxScript.php?upc="+itemID+"&cart="+cart,true);
    httpRequest.send();
  }

  function fillTheCart() {
      try {
        if (httpRequest.readyState === 4) {
          if (httpRequest.status === 200) {
            document.getElementById("cartView").innerHTML=httpRequest.responseText;
          } 
          else {
            alert('There was a problem with the request.');
          }
        }
      }
      catch( e ) {
         alert('Caught Exception: ' + e.description);
      }
  }
}

And here is the script that the ajax calls:

<?php

    //include_once '../databaseFunctions/session.php';
    include_once '../databaseFunctions/databaseConnection.php';
    include_once '../databaseFunctions/databaseFunctions.php';
    include_once '../controller/TableControllerHeader.php';
    include_once '../controller/ShoppingCartControllerHeader.php';
    include_once '../controller/UserControllerHeader.php';
    include_once '../controller/functions.php';

    $upc = intval($_GET['upc']);
    $cartName = $_GET['cart'];

    $cart = new Cart();
    $customer = new Customer();

    print $upc;

    if($upc != ""){
        $cart = addToCart($upc,$cartName);
    }
    else{
        if(isset($_SESSION['customer'])){
            $customer = unserialize($_SESSION['customer']);
            $cart = $customer->FindCart($cartName);
            if($cart = null){
                $cart = new Cart();
            }
        }
    }

    print $cart->PrintCart();

?>

I know that the ajax is working, because the print $cart->PrintCart(); at the end of the script called by ajax is printing what it is supposed to and it is placed in the element with the id "cartView", it just isn't including any data that was supposed to be pulled from the database function.

The localConnection(); function that is called in the itemUPCsearch function is located in the databaseConnection.php script that was included at the beginning of the script that the ajax calls. I am calling that script in my main script as well, but I don't think this is a problem. I don't get any conflict errors, and if I take out the include statement, it gives an error that it can't find the localConnection() function.

I don't understand what is wrong considering everything in the function appears correct. Any help would be greatly appreciated!

Edit

I have printed mysql_error() after each function call in the database function and got no error message after any of them.

Answer 1

Ok, I finally figured out the problem. In the script that the ajax called, I was calling intval($_GET['upc']). The intval function was the problem. Changing it to $upc = $_GET['upc'] fixed the problem.